The present invention relates to fluid conduit systems and, more particularly, to apparatus for coupling ends of a pair of conduits without requiring axial alignment of the conduits.
High pressure air lines or conduits of the type used in, for example, aircraft gas turbine engines, are provided with numerous couplings to permit various sections of an engine to be easily assembled or disassembled. As often occurs with connecting relatively flexible conduits, the ends may not axially align. In order to accommodate potential misalignment, some conduits are provided with a flare and flange arrangement commonly referred to as a Hemsworth fitting. FIG. 1 is a cross-sectional view of a Hemsworth fitting illustrating a conventional method for connecting ends of a pair of conduits 10 and 12. The conduit 10 has a flared end 14 formed with a radiused or arcuate surface at 16. The conduit 12 terminates in an annular flange 18 which has an outer arcuately shaped surface 20 which mates with the surface 16 of conduit 10. The arcuate shape of the surfaces 16 and 20 allows misalignment of the conduits 10 and 12 with respect to each other, i.e., conduit 10 may have an axis
which is not aligned with axis 22 of conduit 12. The phantom lines 24 and 26 indicate off-axis extreme positions of conduit 10 with respect to conduit 12.
The conduits 10 and 12 are retained in an assembled position by a pair of annular couplers 28 and 30 which are similar to a conventional plumbing union. Coupler 28 fits around conduit 10 and has an inner diameter which is less than the extreme outer diameter of flared end 14. The outer circumferential surface of coupler 28 is threaded and fits within and threadingly engages a threaded inner surface of coupler 30. Coupler 30 includes an annular flange 32 which extends adjacent conduit 12 and engages flange 18. When coupler 28 is threaded into coupler 30, coupler 28 reacts against flared end 14 forcing it against flange 18 which is in turn urged toward flared end 14 by flange 32 on coupler 30.
Assembly of the coupling between conduits 10 and 12 requires a pair of spanner wrenches, one to turn coupler 28 and another to turn coupler 30. Coupler 28 has a pair of tabs 34 with holes 36 for receiving pins on a conventional spanner wrench. Typically, coupler 28 is held in a fixed position while coupler 30 is turned. Coupler 30 has a plurality of circumferentially spaced holes 38 for receiving the spanner wrench pins. During this assembly, it is desirable to place a relatively high compressive force on the joint between conduits 10 and 12. An exemplary force is about 4000 pounds compression. In order to produce this force, a torque of about 150 foot-pounds is exerted on the threaded couplers 28 and 30. Not only is this a difficult task to achieve in using a pair of spanner wrenches, the confined quarters in which these couplings are often positioned makes the task more difficult. Accordingly, it is desirable to provide a method and apparatus for assembling a joint between conduit sections which overcomes the above discussed disadvantages of the prior art, specifically, a coupling which: allows axial misalignment of mating high pressure air conduits; and improves ease of installation by reducing the torque level required to achieve adequate compressive force in order to effect a satisfactory seal, eliminating the need for special tooling, and providing for easy access to the tightening means.